When was the last time you ever stopped to have a good think about the giant natural satellite that orbits our planet? The Moon is something that has fascinated us for centuries, but by and large, we have now come to accept it as something that is commonplace within our night sky. Most of us will glance up at it now and again and maybe comment on how bright the Moon or what phase the Moon is currently in. The real question is when was the last time you really thought about the Moon? What is going on under that familiar crater-scarred surface?

“That’s no moon. It’s a space station. ” said Obi Wan Kenobi about the Death Star but this image shows a real natural moon. The lower left part of the image shows a portion of the Moon visible from Earth while the upper right area shows the heavily cratered lunar far side. (Image credit: NASA, image AS16-3021)

Our wondrous satellite has been on our minds recently here at Armagh Planetarium. Did you know that there is a pretty major conspiracy theory out there about our Moon? We know there are conspiracies on almost everything nowadays, but the moon? Fear not, we are here to explain!

A remarkably popular “theory” is the Hollow Moon Hypothesis. The big question that this theory asks is “Is the Moon Hollow?” At this point you are probably furrowing your brow and asking yourself that very question. Many people have asked this, and have been asking it since the first moon landings. However this concept of a hollow Moon isn’t a new one. In his 1901 novel The First Men in the Moon, the great H.G. Wells (1866-1946), known to many as the Father of Science Fiction, wrote about an epic journey to the Moon. His main characters soon find out however that the Moon isn’t all that it seems and that it is hollow and inhabited by a strange insect-like alien race. Quite fantastical for a novel that was published in 1901, but as soon as humans started landing on the Moon over 60 years later, the concept of a Hollow Moon seemed to come to the forefront a little more.

Buzz Aldrin beside the Apollo 11 seismometer. You can use the next diagram to identify its components. (Image credit: Neil Armstrong/NASA)

What started this notion of a hollow Moon? During the lunar landings, the astronauts deployed several seismometers, instruments to record movements and vibrations, into the Moon’s surface and left them there so as to receive data regularly about activities on the moon. These seismometers, which were set up during the Apollo 11, 12, 14, 15 and 16 missions, radioed back information to the Earth until they were finally switched off (to save money!) in 1977.

Schematic diagram of an Apollo seismometer. (Image credit: NASA)

These radio transmissions revealed a lot about the Moon and its internal structure, in particular the existence of moonquakes. These moonquakes were placed into four different categories:
1. Deep Moonquakes (700km below the surface)
2. Vibrations (caused my meteorite impacts)
3. Thermal Quakes
4. Shallow Quakes (20-30km below the surface)

It was the shallow quakes that caused this hare-brained notion of the hollow Moon to come about. It has been said that during these shallow quakes the Moon would “ring like a bell.” This meme of the Moon ringing like a bell first became established in an article written for Popular Science in March 1970. This phrase was used after Apollo 12 purposefully crashed the 2.5 ton Ascent Stage of its Lunar Module onto the Moon’s surface. It was claimed that the Moon rang like a bell for roughly an hour. With information like this, it is no wonder that some people outside of the science community started to think that the Moon might not be as solid as they thought.

A closely-related theory is the Spaceship Moon Theory, or for you science buffs out there, the Vasin-Shcherbakov Theory. This theory takes the concept of a hollow moon one step further into pure science fiction territory. In an article by Michael Vasin and Alexander Shcherbakov published in 1970 it was hypothesised that the Moon was actually an artificial, hollowed out Earth satellite that had been put into place by unknown beings. Vasin and Shcherbakov were members of the then Soviet Academy of Sciences, but the article was published not in a science journal but in Sputnik, a sort of Soviet Reader’s Digest. In the article they refused to speculate what type of unknown beings put the artificial satellite in the Earth’s orbit, but we do think that this is a discussion that should be had at another time. We won’t go too in depth into the finer details of this theory, as we could talk about it for a while, but the general feeling of this article that was produced is that the Moon is made of up everything that a spaceship could be made of, such as materials that can withstand both extreme heat and cold and are extremely tough so could withstand blow from meteorites. Some second hand reporting of Vasin and Shcherbakov’s article claims mica, uranium, brass (a human-made alloy) and neptunium (a radioactive element which does not exist in nature) were discovered in samples returned by Apollo missions but this is not in the original article and is also untrue. Sadly not everything you read on the internet is to be believed.

Alan Shepard on the Moon with the MET, Apollo 14’s unique (but not very useful) pull along trolley. The landscape around him is completely natural. (Image credit: Edgar Mitchell/NASA)

This is a very unlikely theory surrounding the Moon. Now we need to look at some facts about the Moon in order to further our knowledge about it, and help us to decide what we think about these two theories.

Sadly the Moon is not made of cheese. We know this may come as a blow to some of you, but it’s time you know. The Moon is not a giant sphere of cheddar. It does however have a crust, a mantle and a core just like the Earth. In the past decade it has been discovered that the Moon does have an Earth-like core, meaning it would be solid. The core is rich in iron and is solid, with a radius of approximately 150 miles. Then there is a primarily liquid outer core and it has an estimated radius of 205 miles. The Moon’s core differs from the Earth’s by having a partially molten boundary layer. This layer is estimated to have a radius of 300 miles. How was this research conducted to gather this information? By using state of the art seismological techniques and applying this to the same data taken from the first lunar landings, NASA was able to make these discoveries. People who say that the Apollo seismometer results prove that the Moon is hollow have things exactly the wrong way round; the results show that the Moon is a solid body with a variegated internal structure!

What about the mantle, we hear you ask? The mantle is directly under the crust of the Moon (the part that we can visibly see) and it divides the crust from the core. Now to get down to some hard core science (see what we did? Fine…no more bad jokes). It is believed that the mantle of the moon consists of the minerals olivine, orthopyroxene, and clinopyroxene. The actual composition of the Moon’s mantle is very similar to that of the Earth’s, however it is thought that the Moon’s mantle is richer in iron.

To conclude this look into the hollow Moon theories, it is relevant to say from looking at the facts of how the moon is made up that it is probably most likely to be a solid celestial body. Hollow Moon theory can be safely join the Martian canals, planet Vulcan and the Black Knight satellite in the “silly space ideas bin”.

The Moon will always play a large role when it comes to Earth and it will still be the inspiration for many science fiction masterpieces. In fact another idea has recently cropped up in the SF world about the Moon. In the Doctor Who episode Kill the Moon (2014), it was stated that the Moon was actually a giant alien egg! The egg started to crack and a giant alien popped out of it and conveniently laid another Moon-sized egg. Think of that what you will!

40 Comments

Hi, your assertion that the moon has a fluid outer core and a partial melt is contrary to what is stated in an article on NASA’s website here.. https://www.nasa.gov/exploration/home/15mar_moonquakes.html
where it is stated that the moon is dry, cool, and mostly rigid, which is part of their given reason for seismic vibrations to resonate for long periods, and for the moon to “ring like a bell (or gong)”. Such resonance seems reasonable if the moon is actually a more or less solid rock, but less likely if the moon has molten elements in its interior. A molten mantle or outer core would probably absorb and/or help to dissipate seismic vibrations, would it not?
Also, in a book called, “Who Built the Moon?” released in 2006 by authors, Christopher Knight and Allan Butler, they also provide contrary evidence. A description of the book on Amazon states, “The authors of Civilization One return, bringing new evidence about the Moon that will shake up our world. Christopher Knight and Alan Butler realized that the ancient system of geometry they presented in their earlier, breakthrough study works as perfectly for the Moon as it does the Earth. They found a consistent sequence of integer numbers that they can apply to every major aspect of the Moon; no such pattern emerges for any other planet or moon in the solar system. In addition, Knight and Butler discovered that the Moon possesses few or no heavy metals and has no core—something that should not be possible. Their persuasive conclusion: if higher life only developed on Earth because the Moon is exactly what it is and where it is, it becomes unreasonable to cling to the idea that the Moon is a natural object—an idea with profound implications.”
Personally, I do not “believe” anything. I merely look at as much information as I can and develop my own theories, challenging them with new evidence as it comes to hand.
I will make one other point and that is, in regards to the person who claims science does not have an agenda. That is plainly untrue. Science, or more correctly, “modern science” has the agenda of assuring its own relevance and longevity. Most scientists rely on funding from various sources, and thus, they tend to provide answers that will assure their ongoing access to resources and political support. A case in point is the nonsensical climate change scientists, who state things as fact when that are unproven, in order to please their masters, and claim that their work has the backing of thousands of other scientists around the world, when actually, many suitably qualified scientists and researchers wholeheartedly refute the claims they make.
Everyone has an agenda, whether they admit it or not. What is yours?

Hippocrates 460–377 bc. ELLIN physician,and the father of medicine. In his ancient Ellenic-[HELLENIC]-[GREEK] medical writings, writes about the moon and it’s inter-reaction with the earth and the human being,[the fluid parts]. It is most interesting reading, and this knowledge counld come in handy today…

In NASA catalog of lunar events TR R-277 of which your former colleague Patrick Moore was co-author, they recorded yellow streaks of light across crater floors, bright spot on disk when fully eclipsed, appearances of lightning during partial eclipse, smoky gray mist, lunar volcanoes, blinking lights, mingling colours in small spots, etc, etc. Have any of these phenomena ever been explained? Thanks.

Have we taken core samples (drilling into the crust) to empirically prove the moons’ internal geometry and density? Currently it just seems like we are taken educated guesses as to the composition of the moons’ internal structure. I wouldn’t be surprised if we find out we where wrong about the density of the moon in the future when we start building installations on the surface.

Dear Mike, thank you for your comment. However I cannot agree with it. To simulate a sold spherical Moon with a rigid shell requires a material with a combination of density and rigidity that may not even be physically possible. More fundamentally we know the Moon is not hollow. Here are a couple of pieces of evidence. Measurements of the orbit of the Lunar Prospector spacecraft (link) showed that the value of Moon’s normalized polar moment of inertia is 0.393+/-0.001, which is very close to that for a solid object with constant density which is 0.4. Even more telling is that the seismic measurements from the Moon are not those you would see from a hollow object, rather they reveal the internal structure Heather described in her article.

When reading that the Moon is slowly receding from Earth, can one assume pressure/force against the moon is simultaneously changed with the movement?

Yes, that is correct. Eventually the Moon will reach its final position when the Earth and the Moon will be tidally locked to each other, so the same side of the Earth will always face the Moon.This won’t happen for billions of years though.

Could it collapse in on itself due to change in outside pressure/force?

Not really, it’s hard to imagine anything that could do that (apart from science fiction scenarios, for example if a mini black hole was inserted into the Moon’s core).

You’re not the first person to say this here, and I find this hard to answer as it’s not actually true. Where did you hear it?

Impact craters are not all the same depth. Crater depths vary with the diameter of the crater, wider craters are deeper. For smaller craters (less than 15km wide) the depth:diameter ratio is about 1:4 to 1:3. For larger craters, it’s more complex, the depth being proportional to the 0.3 power of their diameter. We see the same relationships across the Solar System (for example on Mercury, Mars, asteroids and moons of Jupiter).

Hello : If the moon is (whole or partially) Hollow, wouldn’t the gravitational forces, ocean tides, etc, between the earth and moon be different. When Apollo 14 ( I may be mistaken which Apollo #) used the “sling shot” effect to get home , would that have been possible if the moon was hollow?
thank you for your time

If the moon is (whole or partially) Hollow, wouldn’t the gravitational forces, ocean tides, etc, between the earth and moon be different.

Surprisingly no. We’ve had a good idea of the relative masses of the Earth and Moon for centuries, and known that the Moon’s average density is a bit more than half that of Earth. The “hollow Moon” idea assumes that this discrepancy indicates that the Moon’s interior is partially empty.

When Apollo 14 ( I may be mistaken which Apollo #) used the “sling shot” effect to get home , would that have been possible if the moon was hollow?

Any kind of orbital maneuver planned around a “solid” Moon would be possible around a hollow Moon but there would be measurable deviations because the calculations necessary make assumptions about how mass is distributed inside the Moon. If the Moon was hollow this would have been obvious as soon as the first spacecraft did a close flyby or went into orbit around it. Scientists have learned about the internal structure of moons of Mars, Jupiter and Saturn by carefully tracking spacecraft flying by them and looking for deviations from the theoretical trajectories. These deviations can be used to calculate how these moons’ interiors are laid out.

I recently watched an episode of Ancient Aliens on the History channel that presented the Hollow Moon theory. It seemed outlandish and in doing some fact checking it brought me to this webpage. I am fascinated by documentaries on the universe going back to Carl Sagan’s Cosmos. It helps when scientists like Neil deGrasse Tyson, Michio Kaku, and Brian Greene, to name a few, bring the complexities of the universe down to a layman’s level. As one studies the vastness of the universe the question always arises, “Are we alone in the universe?” If the answer is no, what logically follows is have we been visited? I have seen where a significant percentage of people believe in UFOs and is reflected not only in Hollywood but throughout science fiction literature for decades. Also you have projects like SETI, the Hubble telescope, and Kepler’s search for earth-like planets not to mention people’s interest in planetariums such as yours. It doesn’t surprise me how such conspiracies arise commingling mythology and conjecture with science and the popularity of these type of shows on the science and history channels. I don’t think the study of religion and science are mutually exclusive. Is there a God and if so did that person create the Big Bang and has subsequently had a role in the universe since the creation. One interesting point made was the size of the sun and the moon relative to their distance to allow for a total eclipse of the sun and the odds this would happen naturally. Thank you for this well written article.

Nice Post Bro, good job friend! I believe in this think also i believe in the Hollow Earth Theory! I have one blog about this thinks.. If you want to know more about, click in my name. Thanks for you time!

This “Hollow Moon Theory” is not new at all.
In fact, it is as old as any history we have.
Zulu’s believe that their gods came from distant solar systems in the hollowed out planetoid and that the “death star” of sorts wreaked all types of havoc on this earth.
The Sumerians also believed the moon to be the vessel that brought the Annunaki.
What fascinates me about this whole hogwash is the fact that the craters are all the same depth and that NASA smudges and fakes photos of the moon.
One more thing that indicates to me that there is some major coverup..
We see a plethora of vividly colored images of nebulas and galaxies and gas clouds from way off in deep space.
But only black and whites of our closest revolving rock. Why?
I guess you would probably say I am ignorant to believe this stuff, I would say you are ignorant to not.

Dear Jingles, thank you for your comments. They prompt me to ask some questions of you.

Zulu’s believe that their gods came from distant solar systems in the hollowed out planetoid

This seems somewhat difficult to believe. Can you provide a link to a reputable source on Zulu culture which confirms this?

The Sumerians also believed the moon to be the vessel that brought the Annunaki.

Again this seems somewhat difficult to believe, but you ought to be able to prove this. Every surviving word written by the Sumerians has been translated into English and put on line (http://etcsl.orinst.ox.ac.uk/). Can you show me where this was said?

…the fact that the (lunar) craters are all the same depth…

Sorry but this not correct, why do you think this is the case?

NASA smudges and fakes photos of the moon

This isn’t correct either, can you show me one of these “faked images”? By the way NASA is not the only organisation to have photographed the Moon.

We see a plethora of vividly colored images of nebulas and galaxies and gas clouds from way off in deep space.
But only black and whites of our closest revolving rock. Why?

Various deep space objects are actually intrinsically colourful while the Moon’s tones are relatively subdued. However there are lots of colour images of the Moon including those taken on Apollo missions. Perhaps you have only seen images from missions like Lunar Orbiter and LRO, these are essentially mapping missions so B&W imagery is perfectly acceptable.

The Moon is a fascinating object but by just accepting myths and rumors about it you are not really learning anything. The Wikipedia article on the Moon (link) is actually fairly good, you could start your research with it.

Dear Gary, thank you for your questions. By “odd rotation” do you mean the Moon’s almost synchronous rotation with the Earth? If so, this is not a mystery; the Moon has become tidally locked with the Earth, every large Moon in the Solar System has a similar relationship with its planet. It would be strange if the Moon didn’t rotate like this!

IT IS BEYOND ME HOW ANYONE CAN THINK THAT THE MOON IS HOLLOW. If the moon was hollow that would mean much less mass which means the geometry of the orbital time verses the weight of the moon can’t orbit in the time it takes. Do the math. Especially since John Lear says there is more gravity there on the moon than what is officially documented. Too many contradictions. The moon is no different than any other moon in this solar system, of course there are some variations in the make up of the moons but basically the mass make up is about the same. Thanks for your time.

Dear Mark, thank you for your comments. Unfortunately I need to correct some of them.

If the moon was hollow that would mean much less mass which means the geometry of the orbital time verses the weight of the moon can’t orbit in the time it takes

That’s not actually correct, the period of a satellite’s orbit (in this case the Moon’s) is determined by the mass of its primary (in this case the Earth) not the satellites mass.

Especially since John Lear says there is more gravity there on the moon than what is officially documented. Too many contradictions.

We’ve accurately known the mass of the Moon for centuries (if it was greater than believed the tides in the oceans would be higher!) John Lear (who I believe claims that the Moon has a dense atmosphere and is inhabited by human-like beings as are Mars and Venus) seems to be an unreliable source for astronomical information!

Great article and it educated me a lot on the subject but couldn’t the moon being way older than earth support the idea of the moon being a hollow object? Can we prove the moon was always at that spot? science also supports the Big Bang theory and obviously the moon was formed by it if it were much older. When did the moon arrive to its current place/orbit? What made it stop from crashing into earth? Could it just be a spaceship developed but advanced beings to withstand all sort of things in space? There are drawings and sculptures in the south of Iraq of Giant winged beings that landed on earth and created us, at least according to what they believed. Them being giant, winged and being far advanced doesn’t proof they could build a giant moon/spaceship but it surely helps it? I would love to read more about the subject. The possibility of the moon being hallow would further many theories I have about What we are, where we came from and and possibly religion. Making sure I have concrete evidence is a bit more than interesting to me

We can measure the Moon’s distance to centimetre accuracy (thanks to retroreflectors left on Moon by space missions) and we know that it is gradually receding from Earth, so the Moon was closer in the past.

science also supports the Big Bang theory and obviously the moon was formed by it if it were much older.

The Moon and the rest of the Solar System formed about 9 billion years after the Big Bang, the Moon is not much older than the Earth.

Could it just be a spaceship developed but advanced beings to withstand all sort of things in space?

Sadly there is exactly zero evidence to support this theory.

There are drawings and sculptures in the south of Iraq of Giant winged beings that landed on earth and created us, at least according to what they believed. Them being giant, winged and being far advanced doesn’t proof they could build a giant moon/spaceship but it surely helps it?

I am afraid that you have been misinformed. There is again zero evidence of this. Winged bulls with human heads were a popular motif in the ancient art of the peoples of modern Iraq but calling them “winged beings” sounds like someone’s attempt to frame them in a science fiction rather than mythological context.

An older surface date is irrelevant. The earth has an active crust so younger features should seem obvious. Science has no agenda. Alien conspiracy is big business. The science channel and Hstory channel make much money on these fantasies. The moon is not hollow. It is easy to prove. Physics are not malleable.

Isn’t mass and gravity involved here? Would a hollow moon produce ocean tides and also be capable of producing gradual changes in the shape of earth’s crust? Let it be known that there is no stronger interaction between our Earth-Moon than that between any other couplet in our system.

Dear Fritzwilliam, thanks for your comments. All I can say is that the people who believe that the the Moon is a hollow sphere tend to have very odd views about gravity and the history of the Earth and Moon!

‘Our Mysterious Spaceship Moon’ by Don Wilson was published in 1977 and was based on the theory. Additional evidence included the moon’s near-circular orbit and, um, aliens. Vastly entertaining. The five-star reviews on Amazon are also entertaining.

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Hello, I’m Heather, welcoming you to Astronotes, the Armagh Observatory and Planetarium’s official blog. Here you will find the latest news and views from all those who work in our organisation, from the fascinating worlds of astronomy and space exploration. We hope you will come here to learn what is hot and exciting, profound or even weird from worlds beyond ours .
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Armagh Observatory opened in 1790

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Director of Armagh Observatory and Planetarium Michael Burton, on top of Mopra Rock in the Warrumbungles National Park of New South Wales. The 22m diameter Mopra radio telescope, star of the tale told here, lies below and behind him. (image credit: Michael Burton)